The present invention involves a control system for enabling telephone answering services to be provided to various telephone extensions within a PBX system for handling of incoming calls from a telephone central office.
In order to provide each of the telephone extensions of a PBX system with telephone answering services, a control system has been interconnected between the PBX system and each of the telephone extension lines. This control system monitors each of the incoming calls received on the telephone extension lines and either allows the transfer of such calls to the various extensions within the PBX system or answers such calls.
In order to enable each of the end users within the PBX system to obtain telephone answering services, it has been necessary to place across each of the extension lines in the PBX system a tip/ring monitor for counting the number of rings on the extension line in the PBX system. Thus, each end user, or subscriber, in the PBX system is able to select the number of rings after which the telephone answering service coupled to the control system will answer the incoming call directed to such subscriber. In order to accomplish this, the number of rings on the subscriber line has been counted and then after a certain number of rings has been reached without the subscriber answering his phone, i.e. without the phone going off-hook, the call has then been transferred to the telephone answering service. In order to monitor the number of rings on a subscriber line, it is necessary to place across each of the extension lines a tip/ring scanner or monitor.
An example of a telephone answering system that can be used in such arrangement or in conjunction with the present invention is the EVE system sold by AMTEL Communications, Inc.
Direct inward dialing DID was brought about to allow a caller to bypass the bottleneck of the switchboard and call directly to a person's desk or an area of interest in a company office or plant. For this purpose, an incoming DID trunk line sends the desired destination extension number to the PBX for automatically distributing an incoming call to the appropriate telephone within a PBX system. These DID numbers that come in on the DID trunk lines are very inexpensive as compared to ordinary telephone numbers that are rented from the telephone company. It is common for many businesses to order 100 numbers at a time. When 100 numbers are ordered, however, usually just a few pair of wires (access lines) need to be provided from the telephone company to the numbers actually being served within the business location.
A series connected telephone answer system that is connected to terminals in the main switching frame of TELCO (telephone central office) is disclosed in commonly assigned U.S. patent application Ser. No. 285,938 to Curtin filed July 23, 1981.